Methods for adjusting the power of an external reader

ABSTRACT

Disclosed herein are methods and systems for adjusting the power level of an external reader of an electronic device. The external reader transmits power to the electronic device with a radio frequency electromagnetic signal. The electronic device may rectify the radio frequency electromagnetic signal and create a rectified voltage. The rectified voltage may be positively correlated to the power level transmitted by the external device. The rectified power can be used to power a component of the electronic device, such as a component configured to measure either a voltage or power associated with the rectified voltage. The electronic device may communicate the measured voltage or power back to the external reader. Based on the communicated voltage or power, the external reader may adjust its power level of the transmitted power.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 14/143,596, entitled “Methods for Adjusting the Power of anExternal Reader,” filed Dec. 30, 2013, the entirety of which isincorporated by reference herein.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Some electronic devices are of sufficiently small size that a powersupply cannot reasonably accompany the device. In these instances, theelectronic device may receive power from an external power source. Theexternal power source may be configured to supply power to theelectronic device wirelessly.

SUMMARY

One aspect of the present disclosure provides an apparatus. Theapparatus includes an antenna configured to receive electromagneticradiation to form a supply signal. The antenna is also configured tooutput a backscatter signal based on the received electromagneticradiation. The antenna also can adjust an antenna impedance to cause abackscatter of the received electromagnetic radiation. The apparatusalso includes a rectifier configured to rectify the supply signal into asupply voltage. Further, the apparatus includes a power unit configuredto measure the supply voltage. Additionally, the apparatus may include ameasurement unit configured to cause the antenna impedance tocommunicate the measured supply voltage via the backscatter of receivedelectromagnetic radiation.

Another aspect of the present disclosure provides reader apparatus. Thereader apparatus includes an antenna configured to transmitelectromagnetic radiation with a power level. The antenna also isconfigured to receive backscatter electromagnetic radiation and output avoltage-indication signal based on the backscatter electromagneticradiation. The reader apparatus also includes a control unit. Thecontrol unit may be configured to analyze the voltage-indication signalto determine a voltage of a device that caused the backscatterelectromagnetic radiation. The control unit may also be configured todetermine a voltage requirement for the device. Further, the controlunit may also be configured to responsively adjust the power level basedon the voltage requirement.

In yet another aspect of the present disclosure, a method is provided.The method includes receiving electromagnetic radiation with an antennato form a supply signal. The method also includes rectifying the supplysignal into a supply voltage. Another part of the method includesmeasuring the supply voltage with a measurement unit. Additionally, themethod includes adjusting an antenna impedance based on the measuredsupply voltage to cause a backscatter of the received electromagneticradiation. The backscatter of the received electromagnetic radiation isbased on both the received electromagnetic radiation and the antennaimpedance.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system that includes aneye-mountable device in wireless communication with a reader, inaccordance with an example embodiment.

FIG. 2A is a bottom view of an example eye-mountable device, inaccordance with an example embodiment.

FIG. 2B is a side view of the example eye-mountable device shown in FIG.2A, in accordance with an example embodiment.

FIG. 2C is a side cross-section view of the example eye-mountable deviceshown in FIGS. 2A and 2B while mounted to a corneal surface of an eye.

FIG. 2D is a side cross-section view of the example eye-mountable devicewhen mounted as shown in FIG. 2C, in accordance with an exampleembodiment.

FIG. 3 is a functional block diagram of an example system for measuringa supply voltage, in accordance with an example embodiment.

FIG. 4 is a block diagram of an electrical sensor system operated by areader to obtain a series of supply voltage measurements over time, inaccordance with an example embodiment.

FIG. 5 shows an example wearer wearing two eye-mountable devices, aband, earrings, and a necklace, in accordance with an exampleembodiment.

FIG. 6 shows a scenario where a reader communicates with aneye-mountable device and a display device, in accordance with an exampleembodiment.

FIG. 7 is a flow chart of an example method, in accordance with anexample embodiment.

DETAILED DESCRIPTION

One aspect of the present disclosure provides a method for adjusting thepower level of an external reader of an electronic device, such as acontact lens with integrated electronics. The external reader transmitspower to the electronic device with a radio frequency electromagneticsignal. The electronic device may rectify the radio frequencyelectromagnetic signal and create a rectified voltage. The rectifiedvoltage may be positively correlated to the power level transmitted bythe external device. This rectified power may be used to power variouscomponents of the electronic device. The rectified power can also beused to power a sensor of the electronic device configured to measureeither a voltage or power associated with the rectified voltage. Theelectronic device may communicate the measured voltage or power back tothe external reader. Based on the communicated voltage or power, theexternal reader may adjust its power level of the transmitted power.

Several benefits may be achieved by adjusting the transmitted powerlevel of the external reader. First, the battery of the external readermay be preserved. The external reader may reduce the power leveltransmitted, thus reducing the amount of battery power used, while stillcontinuing to maintain functionality of the electronic device. Second,the amount of electromagnetic power that is coupled into the body of aperson using the electronic device may be minimized. In someembodiments, the electronic device is part of an eye-mountable device.The power level of the external reader may be chosen to minimize theamount of energy that propagates into the eye of a wearer of theeye-mountable device. Third, the power level transmitted may be reducedin order to prevent the power from interfering (e.g., jamming) nearbyelectronic devices operating with the same wireless frequency and/ortechnology. Fourth, if the power level from the external device is toohigh, the external device may have trouble receiving signals from theelectric device. The power may be high enough that the signalscommunicated from the electronic device back to the external reader maybe drowned out.

An external reader device or “reader” can radiate radio frequencyradiation to power the sensor. The reader may thereby control theoperation of the sensing platform by controlling the supply of power tothe sensing platform. In some examples, the reader can operate tointermittently interrogate the sensing platform to provide a reading byradiating sufficient radiation to power the sensing platform to obtain ameasurement and communicate the result.

The external reader may also include processing logic. The externalreader may receive an indication of a voltage from the electric deviceand compare the voltage to the voltage required for certainfunctionality of the electronic device. For example, some functionalityof the external device may run on 3.4 Volts while other functionalitymay require 5 Volts for correct operation. Therefore, when the externalreader receives an indication of the voltage of the electronic device,it may be able to adjust its transmitted power to increase (or decrease)the voltage of the electronic device.

The sensor of the ophthalmic sensing platform can be configured with, orbe part of, a Radio-frequency Identification (RFID) tag. The RFID tagand reader can communicate using an RFID protocol; e.g., an RFIDGeneration 2 protocol. The RFID tag can be configured to receive radiosignals from the reader. In some embodiments, the reader's signals canbe used for both communicating with and powering the RFID tag; while inother embodiments, the RFID tag can be a powered device; e.g., beconfigured with a battery that powers the tag. In embodiments, where abattery powers the tag, the reader's signals may be used to charge thebattery. Therefore, the battery may be wirelessly charged in situ.

The reader can communicate with other devices than the RFID tag. As onepossible example, the reader can be equipped with a Bluetooth interfaceas well as with an RFID interface. The reader can communicate with otherdevices, e.g., a display device, via a Bluetooth or other protocol. Inone example, the reader can obtain data from the RFID tag using RFIDcommand(s); e.g., the RFID Generation 2 standard Read command. Uponobtaining the data, the reader can store, process, and/or communicatethe data using the Bluetooth interface to another device, such as thedisplay device. Other interfaces for communicating with devices usingother communication protocol(s) are possible as well.

As an example, the above-mentioned contact lens can be configured with asensor that includes an RFID tag. As mentioned above, the sensor can beconfigured to take measurements while being worn in an eye of a wearer.Upon taking the measurements, the sensor may store data related to themeasurements, and subsequently send the data upon request from thereader. The reader, in turn, can store and/or process the received data.For example, the sensor can take current measurements of a supplyvoltage in the tag. The reader can process the supply voltage data todetermine if the supply voltage is large enough to power variouscomponents of the tag. The determination may be based on a desiredfunctionality of the tag.

In some embodiments, the supply voltage information can be sent from thereader to a display device. The display device could be, for example, awearable, laptop, desktop, handheld, or tablet computer, a mobile phone,or a subsystem of such a device. The display device can include aprocessing system; e.g., a central processing unit (CPU), and anon-transitory computer readable medium configured to store at leastprogram instructions. One example of a wearable computer is ahead-mountable display (HIVID). The HIVID can be a device that iscapable of being worn on the head and places a display in front of oneor both eyes of the wearer. The display device can store the datareceived from the reader, perhaps process the data, and generatedisplay(s) based on the received and/or processed data.

In some embodiments, the reader and the display device can be configuredwith configuration data to perform supply voltage processing. Forexample, the reader can include configuration data such as currentmeasurement data for various levels of the supply voltage. Based on thisconfiguration data, the reader can determine if the supply voltage ishigh enough to power various components of the tag. Also, the wearer mayprovide an input to the display device to indicate a desiredfunctionality of the tag. Based on the desired functionality of the tag,a threshold supply voltage may be needed.

During operation of these embodiments, the RFID tag in an eye of thewearer can generate supply voltage data and send the supply voltage datato the reader. The reader can then process the supply voltage data tocompare it with a threshold supply voltage based on a desiredfunctionality of the tag. Then, the display device can be configured toadjust a power level of the signal transmitted from the reader to thetag. In particular embodiments, either the reader or the display devicecan take supply voltage data as inputs and adjust a power level of thesignal transmitted from the reader to the tag as output; i.e., allprocessing can take place at either the reader or display device.

In some embodiments, the reader can be configured to be worn inproximity to one or more contact lenses configured with sensors worn bya person. For example, the reader can be configured to be part of a pairof eyeglasses, jewelry (e.g., earrings, necklace), headband, head coversuch as a hat or cap, earpiece, other clothing (e.g., a scarf), and/orother devices. As such, the reader can provide power and/or receivemeasurements while proximate to the worn contact lens(es).

In other embodiments, both the display and the reader may be combinedinto a single unit. For example, a device, such as a mobile phone, mayhave functionality to act as both the display and the reader to interactwith the tag.

Configuring the reader to be frequently worn in proximity to one or morecontact lenses enables the lenses to have a reliable external powersource and/or storage for sensor data collection, processing of sensordata, and transmission of unprocessed and/or processed sensor data toadditional devices; e.g., the above-mentioned display device. Thus, theherein-described reader can provide valuable support functionality,including but not limited to power, communication, and processingresources, to enhance use of contact lenses with embedded sensors, whileenabling consequent reduction of support functions on the contact lens.This reduction of support functions on the contact lens may freeresources on the contact lens to enable addition of more and/ordifferent sensors and to provide for other functionality on the contactlens.

FIG. 1 is a block diagram of a system 100 that includes an eye-mountabledevice 110 in wireless communication with a reader 180. The exposedregions of the eye-mountable device 110 are made of a polymeric material120 formed to be contact-mounted to a corneal surface of an eye. Asubstrate 130 is embedded in the polymeric material 120 to provide amounting surface for a power supply 140, a controller 150, voltagesensor 160, and a communication antenna 170. The voltage sensor 160 maybe operated by the controller 150 or it may operate based on receivingthe DC Power 141. The power supply 140 supplies operating voltages tothe controller 150 and/or the voltage sensor 160. The antenna 170 isoperated by the controller 150 to communicate information to and/or fromthe eye-mountable device 110. The antenna 170, the controller 150, thepower supply 140, and the voltage sensor 160 can all be situated on theembedded substrate 130. Because the eye-mountable device 110 includeselectronics and is configured to be contact-mounted to an eye, it isalso referred to herein as an ophthalmic electronics platform.

To facilitate contact-mounting, the polymeric material 120 can have aconcave surface configured to adhere (“mount”) to a moistened cornealsurface (e.g., by capillary forces with a tear film coating the cornealsurface). Additionally or alternatively, the eye-mountable device 110can be adhered by a vacuum force between the corneal surface and thepolymeric material due to the concave curvature. While mounted with theconcave surface against the eye, the outward-facing surface of thepolymeric material 120 can have a convex curvature that is formed to notinterfere with eye-lid motion while the eye-mountable device 110 ismounted to the eye. For example, the polymeric material 120 can be asubstantially transparent curved polymeric disk shaped similarly to acontact lens.

The polymeric material 120 can include one or more biocompatiblematerials, such as those employed for use in contact lenses or otherophthalmic applications involving direct contact with the cornealsurface. The polymeric material 120 can optionally be formed in partfrom such biocompatible materials or can include an outer coating withsuch biocompatible materials. The polymeric material 120 can includematerials configured to moisturize the corneal surface, such ashydrogels and the like. In some embodiments, the polymeric material 120can be a deformable (“non-rigid”) material to enhance wearer comfort. Insome embodiments, the polymeric material 120 can be shaped to provide apredetermined, vision-correcting optical power, such as can be providedby a contact lens.

The substrate 130 includes one or more surfaces suitable for mountingthe voltage sensor 160, the controller 150, the power supply 140, andthe antenna 170. The substrate 130 can be employed both as a mountingplatform for chip-based circuitry (e.g., by flip-chip mounting toconnection pads) and/or as a platform for patterning conductivematerials (e.g., gold, platinum, palladium, titanium, copper, aluminum,silver, metals, other conductive materials, combinations of these, etc.)to create electrodes, interconnects, connection pads, antennae, etc. Insome embodiments, substantially transparent conductive materials (e.g.,indium tin oxide) can be patterned on the substrate 130 to formcircuitry, electrodes, etc. For example, the antenna 170 can be formedby forming a pattern of gold or another conductive material on thesubstrate 130 by deposition, photolithography, electroplating, etc.Similarly, interconnects 151, 157 between the controller 150 and thevoltage sensor 160, and between the controller 150 and the antenna 170,respectively, can be formed by depositing suitable patterns ofconductive materials on the substrate 130. A combination ofmicrofabrication techniques including, without limitation, the use ofphotoresists, masks, deposition techniques, and/or plating techniquescan be employed to pattern materials on the substrate 130. The substrate130 can be a relatively rigid material, such as polyethyleneterephthalate (“PET”) or another material configured to structurallysupport the circuitry and/or chip-based electronics within the polymericmaterial 120. The eye-mountable device 110 can alternatively be arrangedwith a group of unconnected substrates rather than a single substrate.For example, the controller 150 and a voltage sensor 160 can be mountedto one substrate, while the antenna 170 is mounted to another substrateand the two can be electrically connected via the interconnects 157.

In some embodiments, the voltage sensor 160 (and the substrate 130) canbe positioned away from the center of the eye-mountable device 110 andthereby avoid interference with light transmission to the central,light-sensitive region of the eye. For example, where the eye-mountabledevice 110 is shaped as a concave-curved disk, the substrate 130 can beembedded around the periphery (e.g., near the outer circumference) ofthe disk. In some embodiments, however, the voltage sensor 160 (and thesubstrate 130) can be positioned in or near the central region of theeye-mountable device 110. Additionally or alternatively, the voltagesensor 160 and/or substrate 130 can be substantially transparent toincoming visible light to mitigate interference with light transmissionto the eye. Moreover, in some embodiments, the voltage sensor 160 caninclude a pixel array (not shown) that emits and/or transmits light tobe received by the eye according to display instructions. Thus, thevoltage sensor 160 can optionally be positioned in the center of theeye-mountable device so as to generate perceivable visual cues to awearer of the eye-mountable device 110, such as by displayinginformation (e.g., characters, symbols, flashing patterns, etc.) on thepixel array.

The substrate 130 can be ring-shaped with a radial width dimensionsufficient to provide a mounting platform for the embedded electronicscomponents. The substrate 130 can have a thickness sufficiently small toallow the substrate 130 to be embedded in the polymeric material 120without influencing the profile of the eye-mountable device 110. Thesubstrate 130 can have a thickness sufficiently large to providestructural stability suitable for supporting the electronics mountedthereon. For example, the substrate 130 can be shaped as a ring with adiameter of about 10 millimeters, a radial width of about 1 millimeter(e.g., an outer radius 1 millimeter larger than an inner radius), and athickness of about 50 micrometers. The substrate 130 can optionally bealigned with the curvature of the eye-mounting surface of theeye-mountable device 110 (e.g., convex surface). For example, thesubstrate 130 can be shaped along the surface of an imaginary conebetween two circular segments that define an inner radius and an outerradius. In such an example, the surface of the substrate 130 along thesurface of the imaginary cone defines an inclined surface that isapproximately aligned with the curvature of the eye mounting surface atthat radius.

The power supply 140 is configured to harvest ambient energy to powerthe controller 150 and voltage sensor 160. For example, aradio-frequency energy-harvesting antenna 142 can capture energy fromincident radio radiation. Additionally or alternatively, solar cell(s)144 (“photovoltaic cells”) can capture energy from incoming ultraviolet,visible, and/or infrared radiation. Furthermore, an inertial powerscavenging system can be included to capture energy from ambientvibrations. The energy harvesting antenna 142 can optionally be adual-purpose antenna that is also used to communicate information to thereader 180. That is, the functions of the communication antenna 170 andthe energy harvesting antenna 142 can be accomplished with the samephysical antenna.

A rectifier/regulator 146 can be used to condition the captured energyto a stable DC supply voltage 141 that is supplied to the controller150. For example, the energy harvesting antenna 142 can receive incidentradio frequency radiation. Varying electrical signals on the leads ofthe antenna 142 are output to the rectifier/regulator 146. Therectifier/regulator 146 rectifies the varying electrical signals to a DCvoltage and regulates the rectified DC voltage to a level suitable foroperating the controller 150. Additionally or alternatively, outputvoltage from the solar cell(s) 144 can be regulated to a level suitablefor operating the controller 150. The rectifier/regulator 146 caninclude one or more energy storage devices to mitigate high frequencyvariations in the ambient energy gathering antenna 142 and/or solarcell(s) 144. For example, one or more energy storage devices (e.g., acapacitor, an inductor, etc.) can be connected in parallel across theoutputs of the rectifier 146 to regulate the DC supply voltage 141 andconfigured to function as a low-pass filter.

The controller 150 is turned on when the DC supply voltage 141 isprovided to the controller 150, and the logic in the controller 150operates the voltage sensor 160 and the antenna 170. The controller 150can include logic circuitry configured to operate the voltage sensor 160so as to interact with the antenna 170 to control the impedance of theantenna 170. The impedance of the antenna 170 may be used to communicatevia backscatter radiation. Antenna 170 and backscatter radiation arediscussed further below.

In one example, the controller 150 includes a sensor interface module152 that is configured to interface with the voltage sensor 160. Thevoltage sensor 160 can be, for example, an electrical sensor configuredto provide an output based on an input voltage of the voltage sensor160. A voltage can be applied at the input of the voltage sensor 160.The voltage sensor 160 may responsively create an output based on theinput voltage. However, in some instances the input voltage may not besufficiently high to power the voltage sensor 160. When the inputvoltage is not high enough to power the voltage sensor 160, the voltagesensor 160 may not provide any output. Although the current disclosuregenerally referrers to voltage sensor 160 as sensing a voltage, variousother electrical sensors may be used in the place of voltage sensor 160.For example, a current sensor, a power sensor, or other electricalsensor may be used in the place of the voltage sensor 160 within thecontext of the present disclosure.

The controller 150 can optionally include a display driver module 154for operating a pixel array. The pixel array can be an array ofseparately programmable light transmitting, light reflecting, and/orlight emitting pixels arranged in rows and columns. The individual pixelcircuits can optionally include liquid crystal technologies,microelectromechanical technologies, emissive diode technologies, etc.to selectively transmit, reflect, and/or emit light according toinformation from the display driver module 154. Such a pixel array canalso optionally include more than one color of pixels (e.g., red, green,and blue pixels) to render visual content in color. The display drivermodule 154 can include, for example, one or more data lines providingprogramming information to the separately programmed pixels in the pixelarray and one or more addressing lines for setting groups of pixels toreceive such programming information. Such a pixel array situated on theeye can also include one or more lenses to direct light from the pixelarray to a focal plane perceivable by the eye.

The controller 150 can also include a communication circuit 156 forsending and/or receiving information via the antenna 170. Thecommunication circuit 156 can optionally include one or moreoscillators, mixers, frequency injectors, etc. to modulate and/ordemodulate information on a carrier frequency to be transmitted and/orreceived by the antenna 170. As previously stated, in some examples, theeye-mountable device 110 is configured to indicate an output from avoltage sensor 160 by modulating an impedance of the antenna 170 in amanner that is perceivable by the reader 180. For example, thecommunication circuit 156 can cause variations in the amplitude, phase,and/or frequency of backscatter radiation from the antenna 170, and suchvariations can be detected by the reader 180.

The controller 150 is connected to the voltage sensor 160 viainterconnects 151. For example, where the controller 150 includes logicelements implemented in an integrated circuit to form the sensorinterface module 152 and/or display driver module 154, a patternedconductive material (e.g., gold, platinum, palladium, titanium, copper,aluminum, silver, metals, combinations of these, etc.) can connect aterminal on the chip to the voltage sensor 160. Similarly, thecontroller 150 is connected to the antenna 170 via interconnects 157.

It is noted that the block diagram shown in FIG. 1 is described inconnection with functional modules for convenience in description.However, embodiments of the eye-mountable device 110 can be arrangedwith one or more of the functional modules (“sub-systems”) implementedin a single chip, integrated circuit, and/or physical component. Forexample, while the rectifier/regulator 146 is illustrated in the powersupply block 140, the rectifier/regulator 146 can be implemented in achip that also includes the logic elements of the controller 150 and/orother features of the embedded electronics in the eye-mountable device110. Thus, the DC supply voltage 141 that is provided to the controller150 from the power supply 140 can be a supply voltage that is providedto components on a chip by rectifier and/or regulator components locatedon the same chip. That is, the functional blocks in FIG. 1 shown as thepower supply block 140 and controller block 150 need not be implementedas physically separated modules. Moreover, one or more of the functionalmodules described in FIG. 1 can be implemented by separately packagedchips electrically connected to one another.

Additionally or alternatively, the energy harvesting antenna 142 and thecommunication antenna 170 can be implemented with the same physicalantenna. For example, a loop antenna can both harvest incident radiationfor power generation and communicate information via backscatterradiation.

The reader 180 can be configured to be external to the eye; i.e., is notpart of the eye-mountable device. Reader 180 can include one or moreantennas 188 to send and receive wireless signals 171 to and from theeye-mountable device 110. In some embodiments, reader 180 cancommunicate using hardware and/or software operating according to one ormore standards, such as, but not limited to, a RFID standard, aBluetooth standard, a Wi-Fi standard, a Zigbee standard, etc.

Reader 180 can also include a computing system with a processor 186 incommunication with a memory 182. Memory 182 is a non-transitorycomputer-readable medium that can include, without limitation, magneticdisks, optical disks, organic memory, and/or any other volatile (e.g.RAM) or non-volatile (e.g. ROM) storage system readable by the processor186. The memory 182 can include a data storage 183 to store indicationsof data, such as sensor readings (e.g., from the voltage sensor 160),program settings (e.g., to adjust behavior of the eye-mountable device110 and/or reader 180), etc. The memory 182 can also include programinstructions 184 for execution by the processor 186 to cause the reader180 to perform processes specified by the instructions 184. For example,the program instructions 184 can cause reader 180 to provide a userinterface that allows for retrieving information communicated from theeye-mountable device 110 (e.g., sensor outputs from the voltage sensor160). The reader 180 can also include one or more hardware componentsfor operating the antenna 188 to send and receive the wireless signals171 to and from the eye-mountable device 110. For example, oscillators,frequency injectors, encoders, decoders, amplifiers, filters, etc. candrive the antenna 188 according to instructions from the processor 186.

In some embodiments, reader 180 can be a smart phone, digital assistant,or other portable computing device with wireless connectivity sufficientto provide the wireless communication link 171. In other embodiments,reader 180 can be implemented as an antenna module that can be pluggedin to a portable computing device; e.g., in scenarios where thecommunication link 171 operates at carrier frequencies not commonlyemployed in portable computing devices. In even other embodimentsdiscussed below in more detail in the context of at least FIG. 5, thereader 180 can be a special-purpose device configured to be wornrelatively near a wearer's eye to allow the wireless communication link171 to operate with a low power budget. For example, the reader 180 canbe integrated in a piece of jewelry such as a necklace, earring, etc. orintegrated in an article of clothing worn near the head, such as a hat,headband, etc.

FIG. 2A is a bottom view of an example eye-mountable electronic device210 (or ophthalmic electronics platform). FIG. 2B is an aspect view ofthe example eye-mountable electronic device shown in FIG. 2A. It isnoted that relative dimensions in FIGS. 2A and 2B are not necessarily toscale, but have been rendered for purposes of explanation only indescribing the arrangement of the example eye-mountable electronicdevice 210. The eye-mountable device 210 is formed of a polymericmaterial 220 shaped as a curved disk. In some embodiments, eye-mountabledevice 210 can include some or all of the above-mentioned aspects ofeye-mountable device 110. In other embodiments, eye-mountable device 110can further include some or all of the herein-mentioned aspects ofeye-mountable device 210.

The polymeric material 220 can be a substantially transparent materialto allow incident light to be transmitted to the eye while theeye-mountable device 210 is mounted to the eye. The polymeric material220 can be a biocompatible material similar to those employed to formvision correction and/or cosmetic contact lenses in optometry, such aspolyethylene terephthalate (“PET”), polymethyl methacrylate (“PMMA”),polyhydroxyethylmethacrylate (“polyHEMA”), silicone hydrogels,combinations of these, etc. The polymeric material 220 can be formedwith one side having a concave surface 226 suitable to fit over acorneal surface of an eye. The opposite side of the disk can have aconvex surface 224 that does not interfere with eyelid motion while theeye-mountable device 210 is mounted to the eye. A circular outer sideedge 228 connects the concave surface 224 and convex surface 226.

The eye-mountable device 210 can have dimensions similar to a visioncorrection and/or cosmetic contact lenses, such as a diameter ofapproximately 1 centimeter, and a thickness of about 0.1 to about 0.5millimeters. However, the diameter and thickness values are provided forexplanatory purposes only. In some embodiments, the dimensions of theeye-mountable device 210 can be selected according to the size and/orshape of the corneal surface of the wearer's eye.

The polymeric material 220 can be formed with a curved shape in avariety of ways. For example, techniques similar to those employed toform vision-correction contact lenses, such as heat molding, injectionmolding, spin casting, etc. can be employed to form the polymericmaterial 220. While the eye-mountable device 210 is mounted in an eye,the convex surface 224 faces outward to the ambient environment whilethe concave surface 226 faces inward, toward the corneal surface. Theconvex surface 224 can therefore be considered an outer, top surface ofthe eye-mountable device 210 whereas the concave surface 226 can beconsidered an inner, bottom surface. The “bottom” view shown in FIG. 2Ais facing the concave surface 226. From the bottom view shown in FIG.2A, the outer periphery 222, near the outer circumference of the curveddisk is curved to extend out of the page, whereas the central region221, near the center of the disk is curved to extend into the page.

A substrate 230 is embedded in the polymeric material 220. The substrate230 can be embedded to be situated along the outer periphery 222 of thepolymeric material 220, away from the central region 221. The substrate230 does not interfere with vision because it is too close to the eye tobe in focus and is positioned away from the central region 221 whereincident light is transmitted to the eye-sensing portions of the eye.Moreover, the substrate 230 can be formed of a transparent material tofurther mitigate effects on visual perception.

The substrate 230 can be shaped as a flat, circular ring (e.g., a diskwith a centered hole). The flat surface of the substrate 230 (e.g.,along the radial width) is a platform for mounting electronics such aschips (e.g., via flip-chip mounting) and for patterning conductivematerials (e.g., via microfabrication techniques such asphotolithography, deposition, plating, etc.) to form electrodes,antenna(e), and/or interconnections. The substrate 230 and the polymericmaterial 220 can be approximately cylindrically symmetric about a commoncentral axis. The substrate 230 can have, for example, a diameter ofabout 10 millimeters, a radial width of about 1 millimeter (e.g., anouter radius 1 millimeter greater than an inner radius), and a thicknessof about 50 micrometers. However, these dimensions are provided forexample purposes only, and in no way limit the present disclosure. Thesubstrate 230 can be implemented in a variety of different form factors,similar to the discussion of the substrate 130 in connection with FIG. 1above.

A loop antenna 270, controller 250, and voltage sensor 260 are disposedon the embedded substrate 230. The controller 250 can be a chipincluding logic elements configured to operate the voltage sensor 260and the loop antenna 270. The controller 250 is electrically connectedto the loop antenna 270 by interconnects 257 also situated on thesubstrate 230. Similarly, the controller 250 is electrically connectedto the voltage sensor 260 by an interconnect 251. The interconnects 251,257, the loop antenna 270, and any conductive electrodes (e.g., for avoltage sensor, etc.) can be formed from conductive materials patternedon the substrate 230 by a process for precisely patterning suchmaterials, such as deposition, photolithography, etc. The conductivematerials patterned on the substrate 230 can be, for example, gold,platinum, palladium, titanium, carbon, aluminum, copper, silver,silver-chloride, conductors formed from noble materials, metals,combinations of these, etc.

As shown in FIG. 2A, which is a view facing the convex surface 224 ofthe eye-mountable device 210, voltage sensor 260 is mounted to a side ofthe substrate 230 facing the convex surface 224. In some embodiments,some electronic components can be mounted on one side of the substrate230, while other electronic components are mounted to the opposing side,and connections between the two can be made through conductive materialspassing through the substrate 230.

The loop antenna 270 is a layer of conductive material patterned alongthe flat surface of the substrate to form a flat conductive ring. Insome instances, the loop antenna 270 can be formed without making acomplete loop. For instances, the loop antenna can have a cutout toallow room for the controller 250 and voltage sensor 260, as illustratedin FIG. 2A. However, the loop antenna 270 can also be arranged as acontinuous strip of conductive material that wraps entirely around theflat surface of the substrate 230 one or more times. For example, astrip of conductive material with multiple windings can be patterned onthe side of the substrate 230 opposite the controller 250 and voltagesensor 260. Interconnects between the ends of such a wound antenna(e.g., the antenna leads) can then be passed through the substrate 230to the controller 250.

FIG. 2C is a side cross-section view of the example eye-mountableelectronic device 210 while mounted to a corneal surface 22 of an eye10. FIG. 2D is a close-in side cross-section view enhanced to show theeye-mountable device 210. It is noted that relative dimensions in FIGS.2C and 2D are not necessarily to scale, but have been rendered forpurposes of explanation only in describing the arrangement of theexample eye-mountable electronic device 210. For example, the totalthickness of the eye-mountable device can be about 200 micrometers,while the thickness of the tear film layers can each be about 10micrometers, although this ratio may not be reflected in the drawings.Some aspects are exaggerated to allow for illustration and facilitateexplanation.

The eye 10 includes a cornea 20 that is covered by bringing the uppereyelid 30 and lower eyelid 32 together over the top of the eye 10.Incident light is received by the eye 10 through the cornea 20, wherelight is optically directed to light sensing elements of the eye 10(e.g., rods and cones, etc.) to stimulate visual perception. The motionof the eyelids 30, 32 distributes a tear film across the exposed cornealsurface 22 of the eye 10. The tear film is an aqueous solution secretedby the lacrimal gland to protect and lubricate the eye 10. When theeye-mountable device 210 is mounted in the eye 10, a tear film coatsboth the concave and convex surfaces 224, 226 with an inner layer (alongthe concave surface 226) and an outer layer (along the convex layer224). The tear film layers can be about 10 micrometers in thickness andtogether account for about 10 microliters.

The tear film layers are distributed across the corneal surface 22and/or the convex surface 224 by motion of the eyelids 30, 32. Forexample, the eyelids 30, 32 raise and lower, respectively, to spread asmall volume of tear film across the corneal surface 22 and/or theconvex surface 224 of the eye-mountable device 210. The tear film layeron the corneal surface 22 also facilitates mounting the eye-mountabledevice 210 by capillary forces between the concave surface 226 and thecorneal surface 22. In some embodiments, the eye-mountable device 210can also be held over the eye in part by vacuum forces against cornealsurface 22 due to the concave curvature of the eye-facing concavesurface 226.

As shown in the cross-sectional views in FIGS. 2C and 2D, the substrate230 can be inclined such that the flat mounting surfaces of thesubstrate 230 are approximately parallel to the adjacent portion of theconvex surface 224. As described above, the substrate 230 is a flattenedring with an inward-facing surface 232 (facing concave surface 226 ofthe polymeric material 220) and an outward-facing surface 234 (facingconvex surface 224). The substrate 230 can have electronic componentsand/or patterned conductive materials mounted to either or both mountingsurfaces 232, 234. As shown in FIG. 2D, the voltage sensor 260,controller 250, and conductive interconnect 251 may be mounted on theoutward-facing surface 234. However, in other embodiments, the variouscomponents may also be mounted on the inward-facing surface.

The polymer layer defining the anterior side may be greater than 50micrometers thick, whereas the polymer layer defining the posterior sidemay be less than 150 micrometers. Thus, voltage sensor 260 may be atleast 50 micrometers away from the convex surface 224 and may be agreater distance away from the concave surface 226. However, in otherexamples, the voltage sensor 260 may be mounted on the inward-facingsurface 232 of the substrate 230 such that the voltage sensor 260 arefacing concave surface 226. The voltage sensor 260 could also bepositioned closer to the concave surface 226 than the convex surface224.

FIG. 3 is a functional block diagram of a system 300 for adjusting thepower of an external reader. The system 300 includes an eye-mountabledevice 210 with embedded electronic components in communication with andpowered by reader 180. Reader 180 can also be configured to communicatewith a display device (the display device may or may not be integratedwith the reader 180 as UI 348). Reader 180 and eye-mountable device 210can communicate according to one communication protocol or standard,shown in FIG. 3 as RF Power 341. In one particular embodiment, theprotocol used for RF Power 341 and Backscatter communication 343 is anRFID protocol. The eye-mountable device 210 includes an antenna 312 forcapturing radio frequency (RF) power 341 from the reader 180. Theantenna 312 may also create backscatter communication 343.

The eye-mountable device 210 includes rectifier 314, energy storage 316(that may output unregulated voltage 317), and regulator 318 forgenerating regulated supply voltages 330, 332 to operate the embeddedelectronics. The eye-mountable device 210 includes a voltage sensor 321that may have a sensor interface 320. The eye-mountable device 210includes hardware logic 324 for communicating results from the sensor321 to the reader 180 by modulating the impedance of the antenna 312. Animpedance modulator 325 (shown symbolically as a switch in FIG. 3) canbe used to modulate the antenna impedance according to instructions fromthe hardware logic 324. Similar to the eye-mountable device 110discussed above in connection with FIG. 1, the eye-mountable device 210can include a mounting substrate embedded within a polymeric materialconfigured to be mounted to an eye.

With reference to FIG. 3, in various embodiments, the voltage sensor 321measures either the unregulated voltage 317 or the regulated supplyvoltage 332. In various embodiments, the voltage measured by the voltagesensor 321 may come from different sources. As shown in FIG. 3, theregulator 318 may provide the regulated supply voltage 332 and theenergy storage 316 may provide unregulated voltage 317. However, inother embodiments, only one of the regulated supply voltage 332 and theunregulated voltage 317 may be provided to the voltage sensor 321. Inadditional embodiments, the regulated supply voltage 332 provided to thevoltage sensor 321 may be the same regulated supply voltage 330 thatsupplies power to the hardware logic 324. The connections shown in FIG.3 are one example of possible configurations for the voltage sensor 321.The sensor interface 320 may be configured as a part of the voltagesensor 321 itself. For example, the sensor interface 320 may convert theoutput of the voltage sensor 321 into a format that in understandable bythe hardware logic 324.

In other embodiments, the sensor interface 320 can contain an electricalsensor other than voltage sensor 321. For example, a current sensor, apower sensor, or other electrical sensor may be used in the place of thevoltage sensor 321 within the context of the present disclosure. Theconnections to the sensor interface 320 may change depending on thespecific type of sensor that forms a portion of sensor interface 320.For example, the sensor unit 320 contains a parallel electricalconnection to the hardware logic 324. A current sensor may be placed ina series electrical connection with one of the hardware logic 324,voltage regulator 318, or other component.

The rectifier 314, energy storage 316, and voltage regulator 318 operateto harvest energy from received RF power 341. RF power 341 causes radiofrequency electrical signals on leads of the antenna 312. The rectifier314 is connected to the antenna leads and converts the radio frequencyelectrical signals to a DC voltage. The energy storage 316 (e.g.,capacitor) is connected across the output of the rectifier 314 to filterout high frequency components of the DC voltage. The regulator 318receives the filtered DC voltage (e.g. unregulated voltage 317) andoutputs both a regulated supply voltage 330 to operate the hardwarelogic 324 and a regulated supply voltage 332 to operate the voltagesensor 321 of the sensor interface 320. For example, the supply voltagecan be equivalent to the voltage of the energy storage 316. In anotherexample, the supply voltage can be equivalent to the voltage of therectified DC voltage from the rectifier 314. Additionally, the regulatedsupply voltage 330 can be a voltage suitable for driving digital logiccircuitry, such as approximately 1.2 volts, approximately 3 volts, etc.The voltage needed as the regulated supply voltage 330 may changedepending on a functionality requirement of the logic 324 (or a voltagerequirement of other components of the eye-mountable device 210).Reception of the RF power 341 from the reader 180 (or another source,such as ambient radiation, etc.) causes the regulated supply voltages330, 332 to be supplied to the sensor 320 and hardware logic 324. Whilepowered, the sensor 320 and hardware logic 324 are configured togenerate and measure a voltage (such as either unregulated voltage 317or regulated supply voltages 332) and communicate the results.

The sensor results can be communicated back to the reader 180 viabackscatter radiation 343 from the antenna 312. The hardware logic 324receives the supply voltage from the sensor interface 320 (or thevoltage sensor 321 itself) and modulates (325) the impedance of theantenna 312 in accordance with the supply voltage measured by the sensor320. The antenna impedance and/or change in antenna impedance aredetected by the reader 180 via the backscatter signal 343.

Reader 180 can include an antenna and RF front end 342 and logiccomponents 344 to communicate using a radio protocol, decode theinformation indicated by the backscatter signal 343, provide digitalinputs to a processing system 346 and receive inputs and/or provideoutputs via user interface 348. The radio protocol can be, for example,an RFID protocol. In some embodiments, part or all of eye-mountabledevice 210 can be configured to perform some or all features of an RFIDtag. For example, as shown in FIG. 3, some or all of the componentsshown as tag 370 of eye-mountable device 210 can perform some or allfeatures of an RFID tag; e.g., antenna 312, rectifier 314, energystorage 316, voltage regulator 318, hardware logic 324, etc.

In some embodiments, one or more of the features shown as separatefunctional blocks can be implemented (“packaged”) on a single chip. Forexample, the eye-mountable device 210 can be implemented with therectifier 314, energy storage 316, voltage regulator 318, sensorinterface 320, and the hardware logic 324 packaged together in a singlechip or controller module. Such a controller can have interconnects(“leads”) connected to the loop antenna 312 and the sensor electrodes322, 323. Such a controller operates to harvest energy received at theloop antenna 312, measure the supply voltage created by the harvestedenergy, and indicate the measured supply voltage via the antenna 312(e.g., through the backscatter communication 343).

A processing system, such as, but not limited to, processing system 346or processing system 356, can include one or more processors and one ormore storage components. Example processor(s) include, but are notlimited to, CPUs, Graphics Processing Units (GPUs), digital signalprocessors (DSPs), application specific integrated circuits (ASICs).Example storage component(s) include, but are not limited to volatileand/or non-volatile storage components, e.g., optical, magnetic, organicor other memory, disc storage; Random Access Memory (RAM), Read-OnlyMemory (ROM), flash memory, optical memory unit, and disc memory. Thestorage component(s) can be configured to store software and data; e.g.,computer-readable instructions configured, when executed by a processorof the processing system, to cause the processing system to carry outfunctions such as but not limited to the herein-described functions ofreader 180, eye-mountable device 210, and/or display device 350.

The reader 180 can associate the backscatter signal 343 with the sensorresult (e.g., via the processing system 346 according to apre-programmed relationship associating impedance of the antenna 312with output from the sensor 320). The processing system 346 can thenstore the indicated sensor results (e.g., induced supply voltage) in alocal memory and/or an external memory (e.g., by communicating with theexternal memory either on display device 350 or through a network).

User interface 348 of reader 180 can include an indicator, such as butnot limited to one or more light-emitting diodes (LEDs) and/or speakers,that can indicate that reader 180 is operating and provide someinformation about its status. For example, reader 180 can be configuredwith an LED that displays one color (e.g., green) when operatingnormally and another color (e.g., red) when operating abnormally. Inother embodiments, the LED(s) can change display when processing and/orcommunicating data in comparison to when idle (e.g., periodically turnon and off while processing data, constantly stay on or constantly stayoff while idle). The reader 180 may also provide an audio output basedon the voltage sensor data.

In some embodiments, one or more of the LED(s) of user interface 348 canindicate a status of sensor data; e.g., not display when sensor data areeither within normal range(s) or unavailable, display in a first colorwhen sensor data are either outside normal range(s) but not extremelyhigh or low, and display a second color when the sensor data areextremely high and/or low. For example, if the voltage sensor data isunavailable, it may indicate that the RF Power 341 is too low to inducea voltage in the eye-mountable device 210 to power the voltage sensor321. In another embodiment, the voltage sensor data may indicate thevoltage is too low based on the RF Power 341 being too low to induce avoltage to power a component (or a function) of the eye-mountable device210. In yet another embodiment, the voltage sensor data may indicate thevoltage is too high based on the RF Power 341 being high enough toinduce a voltage power a component (or a function) of the eye-mountabledevice 210, but the voltage is sufficiently higher than needed. In someembodiments, the processing system 346 may responsively adjust the RFPower 341 based on the voltage sensor data.

In some embodiments, reader 180 can communicate with devices in additionto eye-mountable device 210/tag 370. For example, the reader 180 mayalso function as a cellular phone or other mobile device.

FIG. 4 is a block diagram of a system 400 with eye-mountable device 210operated by a reader 180 to obtain a series of supply voltagemeasurements over time. An electrical sensor; e.g., an embodiment ofsensor 321, can be included with eye-mountable device 210. As shown inFIG. 4, eye-mountable device 210 is configured to be contact-mountedover a corneal surface of an eye 10. The ophthalmic electrical sensorcan be operated to be transitioned into an active measurement mode inresponse to receiving a signal from the reader 180.

The reader 180 includes a processing system 346, configured with memory414. The processing system 412 can be a computing system that executescomputer-readable instruction stored in the memory 414 to cause thereader 180/system 400 to obtain a time series of measurements byintermittently transmitting a measurement signal to eye-mountable device210. In response to the measurement signal, one or more sensors ofeye-mountable device 210; e.g., electrical sensor 430, can takemeasurement(s), obtain results of the measurement(s), and communicatethe results to reader 180 via backscatter 422. As discussed aboveregarding FIG. 3, reader 180 can provide RF power, such as RF power 420,to be harvested by the eye-mountable device 210. For example, impedanceof an antenna of eye-mountable device 210 can be modulated in accordancewith the sensor result such that the backscatter radiation 422 indicatesthe sensor results. Reader 180 can also use memory 414 to storeindications of supply voltage measurements communicated by the voltagesensor 430. The reader 180 can thus be operated to intermittently powerthe electrical sensor 430 so as to obtain a time series of supplyvoltage measurements.

FIG. 5 shows an example wearer 500 wearing two eye-mountable devices 210a, 210 b, a band 522, earrings 524 a, 524 b, and a necklace 526. Asdiscussed above at least in the context of FIGS. 3, 4A, and 4B, eacheye-mountable device 210 a, 210 b can be configured with sensor(s) tomeasure at least the supply voltage induced in the respective lens.

The functionality of band 522 can be performed by a structure of anotherdevice, e.g., an eye-glass frame, a head-mountable computer frame, acap, a hat, part of a hat or cap (e.g., a hat band or bill of a baseballcap), a headphone headband, etc., or by a separate band; e.g., a headband, a scarf or bandanna worn as a head band. For examples, band 522can be supported by ear(s), nose, hair, skin, and/or a head of wearer500, and perhaps by external devices e.g., stick pins, bobby pins,headband elastics, snaps. Other and different support(s) for band 522are possible as well.

One or more of band 522, earrings 524 a, 524 b, and necklace 526 can beconfigured to include one or more readers; e.g., the above-mentionedreader 180. FIG. 5 shows three example positions 180 a, 180 b, and 180 cfor readers in band 522. For example, if only eye-mountable device 210 ahas a sensor, then a reader, such as reader 180, can be mounted inexample positions 180 a and/or 180 b to send commands and power toeye-mountable device 210 a. Similarly, to power and communicate with asensor in eye-mountable device 210 b, a reader mounted in band 522, suchas reader 180, can be mounted in example positions 180 b and/or 180 c.

Each of or both earrings 524 a, 524 b can be configured with respectivereaders 180 d, 180 e for communicating with and power sensors inrespective eye-mountable devices 210 a, 210 b. Necklace 526 can beconfigured with one or more readers 180 f, 180 g, 180 h forcommunicating with and power sensors in respective eye-mountable device210 a, 210 b. Other embodiments are possible as well; e.g., readers inpositions 180 a-180 c or near those positions can be configured as partof a hat, headband, scarf, jewelry (e.g., a brooch), glasses, headmounted device, and/or other apparatus.

In some embodiments, a reader can power a sensor in eye-mountable device210 using a low-power transmission; e.g., a transmission of 1 watt orless of power. In these embodiments, the reader can be within apredetermined distance; e.g., 1 foot, 40 cm, of eye-mountable device 210a, 210 b to power the sensor.

FIG. 6 shows a scenario 600 where reader 180 communicates with aneye-mountable device (EMD) 210. In scenario 600, eye-mountable device210 and reader 180 communicate using an RFID protocol; e.g., an RFIDGeneration 2 protocol such as specified in “EPC™ Radio-FrequencyIdentity Protocols Class-1 Generation-2 UHF RFID Protocol forCommunications at 860 MHz-960 MHz, Version 1.2.0”, Oct. 23, 2008,EPCglobal Inc.

In other scenarios, the reader, tag, display device, and/or otherdevice(s) can communicate using different and/or additional protocols;e.g., an IEEE 802.11 protocol (“Wi-Fi”), an IEEE 802.15 protocol(“Zigbee”), a Local Area Network (LAN) protocol, a Wireless Wide AreaNetwork (WWAN) protocol such as but not limited to a 2G protocol (e.g.,CDMA, TDMA, GSM), a 3G protocol (e.g., CDMA-2000, UMTS), a 4G protocol(e.g., LTE, WiMAX), a wired protocol (e.g., USB, a wired IEEE 802protocol, RS-232, DTMF, dial pulse). Many other examples of protocol(s)and combination(s) of protocols can be used as well.

Although scenario 600 in shown in a linear order, the blocks may also beperformed in a different order. Additionally, in some embodiments, atleast one block of scenario 600 may be performed in parallel to anotherblock of scenario 600.

Scenario 600 begins with reader 180 sending communication to theeye-mountable device (EMD) 210 with a transmit RF Power 620. Thetransmitted RF Power 620 may be a radio signal with a defined radiopower. In some embodiments, the radio power may be transmitted as acontinuous wave (CW) radio signal or the radio power may be transmittedas a pulse-modulated radio signal. In other embodiments, the RF Power620 transmission may take a form other than a CW or pulse-modulatedradio signal. In some embodiments, the communication may be aninitialization of the eye-mountable device 210. However, in otherembodiments, the communication may be the normal operation of theeye-mountable device 210.

When the EMD 210 received the RF power 620, it converts the RF power 620into a supply voltage. The supply voltage is used to power variouscomponents within the EMD 210. The EMD 210 may also be configured tomeasure the supply voltage created in the EMD 210. The EMD 210 mayinclude an electrical component configured to measure the supply voltageinduced in the EMD 210 from the RF power 620. Additionally, the EMD 210may be configured to create a backscatter signal based on the measuredsupply voltage 622.

After transmitting RF Power 620 to an EMD 210, the reader 180 mayresponsively receive a Supply Voltage Indication 624 communicated fromthe EMD 210. The EMD may communicate the Supply Voltage Indication 624through backscatter radiation of the RF Power 620. The backscatterradiation may be created by a modulation of an impedance of an antennaof the EMD 210. The EMD 210 may be configured to modulate the antennaimpedance to create a signal to communicate a supply voltage induced inthe EMD 210 by RF Power 620.

Once the Reader 180 receives the Supply Voltage Indication 624, it mayAnalyze the Voltage Indication 626. When the Reader 180 Analyzes theVoltage Indication 626, it may determine a supply voltage that wasinduced in the EMD 210 by the RF power 620. In some embodiments,Analyzing the Voltage Indication 626 may determine that a signalreceived as Supply Voltage Indication 624 does not actually contain anindication of supply voltage. In this instance, the lack of anindication of a supply voltage may indicate to the Reader 180 that thethere is an error in the EMD 210.

Once the Reader 180 Analyzes the Voltage Indication 626, it mayresponsively Determine a Voltage Requirement 628. The Reader 180 mayDetermine a Voltage Requirement 628. The Reader 180 may determine avoltage requirement in several ways. First, the Reader may determine adesired function for the EMD 210. Each desired function may have anassociated voltage requirement. The Reader 180 may compare the voltagerequirement for the desired function of the EMD 210 (or, in an instancewhere the EMD 210 performs multiple functions, the highest voltagerequirement needed for any function). Once the Reader 180 Determines aVoltage Requirement 628, the Reader 180 may compare the voltagerequirement with the voltage indication to determine a differencebetween the Determined Voltage Requirement 626 and the VoltageIndication 626. In other embodiments, the Reader 180 may not have beenable to determine an inducted voltage in the EMD 210 when Analyzing theVoltage Indication 626. In this embodiment, the Reader 180 may determinethat the voltage induced in the EMD 210 is too low to power the voltagesensor.

Once the reader has Determined Voltage Requirement 628 (or determinedthe induced voltage is too low), the reader may transmit to the EMD 120with an Adjusted RF Power 630. If the Determined Voltage Requirement 628is greater than the induced voltage determined by Determined VoltageRequirement 628, then the Adjusted RF Power 628 will be increasedcompared to the RF Power 620. If the Determined Voltage Requirement 628is less than the induced voltage determined by Determined VoltageRequirement 628, then the Adjusted RF Power 630 may be decreasedcompared to the RF Power 620. The Adjusted RF Power 630 does not have tobe decreased in order to power various components of the EMD 210 (as thevoltage is already sufficiently high), but the Adjusted RF Power 630 maybe lowered to both conserve power of the Reader 180 and reduce theamount of RF Power coupled into the body of the person wearing the EMD210. If the Reader 180 determines that the voltage induced in the EMD210 is too low to power the voltage sensor, the Reader 180 may increasethe RF Power when transmitting the Adjusted RF Power 630. Scenario 600may be repeated after the RF Power is adjusted. Other examples ofscenario 600 are possible as well.

FIG. 7 is a flow chart of an example method 700. Method 700 can becarried out by a device, such as a tag in an eye-mountable device, or adevice that includes a processor, such the hardware logic 324, thehardware logic may include a computer readable medium storingmachine-readable instructions, where the machine-readable instructions,when executed by a processing component of the device, are configured tocause the device to carry out some or all of the techniques describedherein as method 700.

Method 700 can begin at block 710. At block 710, the tag can receive RF(i.e. electromagnetic) power, such as discussed above in the context ofat least FIG. 6. An antenna in the tag may receive the RF power andoutput an RF signal (as a voltage). The RF signal may be proportional tothe received RF power. The tag can be part of an eye-mountable device;e.g., tag 370 of eye-mountable device 210, such as discussed above inmore detail in the context of at least FIG. 3. In some embodiments, thereader can be within a predetermined distance from the tag whentransmitting RF power to the tag, such as discussed above in the contextof at least FIG. 5. In other embodiments, the reader can be part of anHMD, such as discussed above in the context of at least FIG. 5.

At block 720, the tag can rectify the RF signal output from the antenna.By rectifying the supply signal, a direct current (DC) supply voltagemay be created. Because the supply signal may be a conversion of thepropagating RF power to a guided electric RF signal, it may havealternating current properties. For example, the amplitude of the supplysignal may vary from a positive voltage to a negative voltage. Afterrectification, the supply voltage does not have an amplitude that swingsfrom positive to negative. Therefore the supply voltage may beconsidered an unregulated DC supply voltage.

Additionally, the rectified supply voltage may also be applied across acapacitor or other electrical storage component. The capacitor (orstorage component) may perform at least one of two functions. First, thecapacitor may store some electrical energy. This electrical energy maybe used to power components of the tag if the RF power is no longerapplied to the antenna of the tag. Second, the capacitor may alsoprovide some smoothing (e.g. low-pass filtering) of the rectifiedvoltage. This smoothing may allow a more consistent supply voltage to besupplied to the various components of the tag.

At block 730, the tag may measure the supply voltage with a measurementunit, such as a voltage sensor. The voltage sensor may be configured touse both the supply power to power itself, as well as measure thevoltage of the supply voltage. In other embodiments, the tag can containan electrical sensor other than a voltage sensor. For example, a currentsensor, a power sensor, or other electrical sensor may be used in theplace of the voltage sensor within the context of the presentdisclosure. If the electronic unit has a sensor other than a voltagesensor, a different electrical property of the supply voltage may bemeasured.

In some embodiments, the supply voltage measured by the voltage sensoris an unregulated voltage. The unregulated voltage may be provided bythe output of the capacitor (or other energy storage device). In otherembodiments, the supply voltage the voltage sensor may measure is aregulated voltage. The regulated voltage may be a voltage that comes outof a regulator component. A regulated voltage may have a more consistentand stable voltage than the unregulated voltage. Additionally, regulatedvoltage may be used to supply power to various components of the device.

At block 740, the tag may adjust an antenna impedance based on themeasured supply voltage. The antenna impedance may be adjusted in a wayto cause a backscatter signal of the RF power. The backscatter signalmay communicate the measured voltage back to a reader device. Therefore,through the impedance adjustment, the tag may communicate the measuredsupply voltage back to the reader.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent methods andapparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent to those skilled in the art from theforegoing descriptions. Such modifications and variations are intendedto fall within the scope of the appended claims.

The above detailed description describes various features and functionsof the disclosed systems, devices, and methods with reference to theaccompanying figures. In the figures, similar symbols typically identifysimilar components, unless context dictates otherwise. The exampleembodiments described herein and in the figures are not meant to belimiting. Other embodiments can be utilized, and other changes can bemade, without departing from the spirit or scope of the subject matterpresented herein. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe figures, can be arranged, substituted, combined, separated, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated herein.

With respect to any or all of the ladder diagrams, scenarios, and flowcharts in the figures and as discussed herein, each block and/orcommunication may represent a processing of information and/or atransmission of information in accordance with example embodiments.Alternative embodiments are included within the scope of these exampleembodiments. In these alternative embodiments, for example, functionsdescribed as blocks, transmissions, communications, requests, responses,and/or messages may be executed out of order from that shown ordiscussed, including substantially concurrent or in reverse order,depending on the functionality involved. Further, more or fewer blocksand/or functions may be used with any of the ladder diagrams, scenarios,and flow charts discussed herein, and these ladder diagrams, scenarios,and flow charts may be combined with one another, in part or in whole.

A block that represents a processing of information may correspond tocircuitry that can be configured to perform the specific logicalfunctions of a herein-described method or technique. Alternatively oradditionally, a block that represents a processing of information maycorrespond to a module, a segment, or a portion of program code(including related data). The program code may include one or moreinstructions executable by a processor for implementing specific logicalfunctions or actions in the method or technique. The program code and/orrelated data may be stored on any type of computer readable medium suchas a storage device including a disk or hard drive or other storagemedium.

The computer readable medium may also include non-transitory computerreadable media such as computer-readable media that stores data forshort periods of time like register memory, processor cache, and randomaccess memory (RAM). The computer readable media may also includenon-transitory computer readable media that stores program code and/ordata for longer periods of time, such as secondary or persistent longterm storage, like read only memory (ROM), optical or magnetic disks,compact-disc read only memory (CD-ROM), for example. The computerreadable media may also be any other volatile or non-volatile storagesystems. A computer readable medium may be considered a computerreadable storage medium, for example, or a tangible storage device.

Moreover, a block that represents one or more information transmissionsmay correspond to information transmissions between software and/orhardware modules in the same physical device. However, other informationtransmissions may be between software modules and/or hardware modules indifferent physical devices.

The particular arrangements shown in the figures should not be viewed aslimiting. It should be understood that other embodiments can includemore or less of each element shown in a given figure. Further, some ofthe illustrated elements can be combined or omitted. Yet further, anexample embodiment can include elements that are not illustrated in thefigures.

It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in thefigures, can be arranged, substituted, combined, separated, and designedin a wide variety of different configurations, all of which areexplicitly contemplated herein. While various aspects and embodimentshave been disclosed herein, other aspects and embodiments will beapparent to those skilled in the art.

Example methods and systems are described above. It should be understoodthat the words “example” and “exemplary” are used herein to mean“serving as an example, instance, or illustration.” Any embodiment orfeature described herein as being an “example” or “exemplary” is notnecessarily to be construed as preferred or advantageous over otherembodiments or features. Reference is made herein to the accompanyingfigures, which form a part thereof. In the figures, similar symbolstypically identify similar components, unless context dictatesotherwise. Other embodiments may be utilized, and other changes may bemade, without departing from the spirit or scope of the subject matterpresented herein. The various aspects and embodiments disclosed hereinare for purposes of illustration and are not intended to be limiting,with the true scope and spirit being indicated by the following claims.

1-20. (canceled)
 21. A method comprising transmitting, by a readerdevice, electromagnetic radiation with a power level, receiving, by thereader device, backscattered electromagnetic radiation as avoltage-indication signal, generating, by the reader device, avoltage-indication signal based on the backscatter electromagneticradiation; determining, by the reader device, a working voltageharvested by a device that caused the backscattered electromagneticradiation; determining, by the reader device, a voltage requirement forthe device based on a function associated with the device; andresponsive to determining the voltage requirement, adjusting the powerlevel based on the voltage requirement and the determined workingvoltage.
 22. The method of claim 21, wherein determining the voltagerequirement is further based on a threshold power requirement for thedevice.
 23. The method of claim 21, wherein determining the voltagerequirement is further based on a function the device will perform. 24.The method of claim 21, wherein adjusting the power level is furtherbased on both the voltage requirement and a power usage of the readerdevice.
 25. The method of claim 21, further comprising, in response tonot receiving backscatter, increasing the power level.
 26. The method ofclaim 21, further comprising, in response to determining the voltage ofthe device is not high enough to power a power unit of the device,increasing the power level of the transmitted electromagnetic radiation.27. The method of claim 21, further outputting a sound based on thevoltage-indication signal.
 28. The method of claim 21, furthercomprising receiving an indication of desired functionality for thedevice, and wherein determining the voltage requirement is further basedon the indication of the desired functionality for the device.
 29. Asystem comprising a reader device, the reader device comprising: anantenna configured to: transmit electromagnetic radiation with a powerlevel, and receive backscattered electromagnetic radiation as avoltage-indication signal and output a voltage-indication signal basedon the backscatter electromagnetic radiation; and a control unitconfigured to: determine a working voltage harvested by a device thatcaused the backscattered electromagnetic radiation based on thevoltage-indication signal; determine a voltage requirement for thedevice based on a function associated with the device; responsive todetermining the voltage requirement, adjust the power level based on thevoltage requirement and the determined working voltage; communicate witha display device; and transmit one or more signals to the displaydevice, the one or more signals indicating the voltage requirement orthe power level.
 30. The system of claim 29, wherein the reader devicecomprises the display device.
 31. The system of claim 29, wherein thereader device is separate from the display device.
 32. The system ofclaim 29, wherein the control unit is further configured to: receive,from the display device, an indication of desired functionality for thedevice, and determine the voltage requirement based on the indication ofthe desired functionality for the device.
 33. The system of claim 29,wherein the reader device is a wearable device.
 34. The system of claim29, wherein the control unit is further configured to access one or moreconfiguration data stored in a memory of the reader device; anddetermine the voltage requirement further based on the configurationdata.
 35. The system of claim 29, wherein the control unit is furtherconfigured to receive sensor data from the device and to store thesensor data in a memory of the reader device.
 36. The system of claim29, wherein the control unit is further configured to receive sensordata from the device and to transmit the received sensor data to thedisplay device.
 37. A display device comprising: a non-transitorycomputer-readable medium; and a processor configured to executeprocessor-executable instructions stored in the non-transitorycomputer-readable medium to: receive a voltage-indication signal from areader device, the voltage-indication signal based on backscatterelectromagnetic radiation received by the reader device from a targetdevice; determine a working voltage harvested by the target device basedon the voltage-indication signal; determine a voltage requirement forthe target device based on a function associated with the target device;and responsive to determining the voltage requirement, cause the readerdevice to adjust a power level of electromagnetic radiation transmittedby the reader device based on the voltage requirement and the determinedworking voltage.
 38. The display device of claim 37, wherein the displaydevice comprises the reader device.
 39. The display device of claim 37,wherein the reader device is separate from the display device.
 40. Thedisplay device of claim 37, wherein the processor is further configuredto execute processor-executable instructions stored in thenon-transitory computer-readable medium to: receive a user inputindicating a desired functionality for the target device, and cause thereader device to change a configuration of the target device based onthe indication of the desired functionality of the target device. 41.The display device of claim 40, wherein the processor is furtherconfigured to execute processor-executable instructions stored in thenon-transitory computer-readable medium to: determine the voltagerequirement based on the indication of the desired functionality for thetarget device.
 42. The display device of claim 37, wherein the displaydevice is a wearable device.
 43. The display device of claim 37, whereinthe processor is further configured to execute processor-executableinstructions stored in the non-transitory computer-readable medium toaccess one or more configuration data, and determine the voltagerequirement further based on the configuration data.
 44. The displaydevice of claim 37, wherein the processor is further configured toexecute processor-executable instructions stored in the non-transitorycomputer-readable medium to receive sensor data from the reader deviceand to store the sensor data in the non-transitory computer-readablemedium.